PPL Corp. said it wants to spend billions of dollars to build a 725-mile system of electric transmission lines that will bring energy from the booming Marcellus Shale natural gas fields to customers on the heavily populated Eastern Seaboard.

The Allentown-based utility said Thursday the 500-kilovolt line would span much of Pennsylvania and reach into New York, New Jersey and Maryland, although the route has not been determined. The cost was expected to exceed $4 billion, and it could take more than a decade to build.

PPL said the project was likely to increase reliability during demand-driven power shortages and save money for customers.

“We don’t have a specific per-megawatt-hour estimate right now, but our analysis shows consumers in these states would save hundreds of millions of dollars per year in power costs,” said PPL Electric Utilities spokesman Paul Wirth.

A rough map produced by the company shows a line running from Pittsburgh through Pennsylvania’s rural northern tier and into the New York City region. A second line branches south through the Susquehanna River corridor into Maryland, while a third spur runs through the Lehigh Valley and Pocono Mountains into central New Jersey.

The project requires regulatory approval, and the company has begun the process with a submission to PJM Interconnection, the regional coordinator for wholesale energy. It also must get the OK of utility regulators in each state, Wirth said.

He said electrical transmission in the Northeast is congested in some areas, a problem the new capacity would help relieve.

Pennsylvania Public Utility spokeswoman Robin Tilley said her agency requires an application that specifies the cost and route and demonstrates it is the best option on a set of criteria that includes safety, environmental impact and effect on scenery, historic places, landscape and wildlife. The PUC will hold public hearings.

PPL said the transmission lines would help develop power plants along its route that would be fueled by natural gas from the Marcellus Shale formation. Wirth said the system would be fed by new gas-fired plants in northern Pennsylvania and by lower-cost power from western Pennsylvania and Ohio.

The company estimates the project’s total cost at $4 billion to $6 billion. If construction begins by 2017, PPL said the work could be complete around 2023-2025.